The reading interface is very nice, and it handled almost every non-DRMed format I threw at it (Mobipocket, RAR files, Palm Doc files). The PDF support is a little funky, and it doesn't seem to support any images beyond the cover image. Other than that, the book display is smooth and peasant to read with, and there are a lot of choices for customizing how the book is displayed (such as multi-column, single column, and vertical scrolling).

The really fantastic part, though, is the iPhone export function! Stanza seems to turn the books into "bookmarklets", which you can then import into Safari and sync with your iPhone (and, presumably, your iPod touch), and then you can read your book by selecting the title and chapter from Safari's bookmarks button on your phone. It even worked in "Airplane Mode" when I turned it on, so it definitely doesn't need to use the network to read the book. The reading interface on the iPhone isn't quite as nice as the desktop version, and there doesn't seem to be any way to adjust anything except the font size and the autoscrolling speed when on the iPhone, but being able to take all my books with me on my iPhone is something that certainly makes this software worth it. And until the iPhone App Store opens, this seems to be the only way to get books onto your phone without jailbreaking it.